Microsoft is currently testing a new Vertical Tabs feature for the Edge browser which they say will help users organize their tabs better.
Microsoft is also working on running PWAs in their own windows and in the current version of Edge Canary and Edge Dev, with selected users, and on some occasions both get tested together.
For those lucky few Microsoft is offering the option, when installing a PWA, of opening the PWA as a tab, a separate window or a tabbed window.
Leo Varela has sent us these images of Tabbed PWAs running in vertical tabbed windows to see what the last option looks like.
Above is the YouTube PWA running in a vertical tab window.
Here is the same site with the vertical tabs collapsed.
Here is the Disqus PWA also running in a vertical tabbed window, and it is notable that the colour of the site Chrome changes with the colour scheme of the website.
At present not all PWAs support the tabbed interface, including Twitter.
With Microsoft still selectively testing vertical tabs it may be some time before the feature rolls out more widely.